Brown algae refers to any members of the scientific class Phaeophyceae. These organisms typically thrive in oceans, including the cold water of the northern Atlantic. Brown algae range in size and structure, forming a diverse class of organisms. Some species of brown algae are edible seaweeds, while others have important commercial uses.
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Different species of brown algae exhibit a range of colors, from dark browns to deep golden hues. Unlike many other plants, these algae do not have true roots or leaves. Rather, a root-like structure attaches to rocks or the seafloor. Stalks grow from this root-like structure and can reach great lengths. Kelps are the largest type of brown algae, sometimes reaching 150 feet in length. These plants have broad leaf-like extensions that grow from the stalks.
All brown algae species are multicellular organisms with different types of tissues. Like all plants, brown algae have cell walls made from cellulose and other rigid polysaccharides. They store sugars, alcohols and other carbohydrates to use for energy. Algae cells contain chlorophyll, beta-carotene and a xanthopyll pigment called fucoxanthin. These chemicals give the plants their characteristic brown color.
Brown algae follow a reproductive life cycle called the alternation of generations. This means that the plants alternate between a diploid and haploid form. Diploid forms contain paired copies of chromosomes, while the haploid forms contain only one copy of each chromosome. In one generation, the brown algae produce spores that grow into new plants, while the next generation produces reproductive cells.
People harvest brown algae to use in a variety of ways. Asian cultures use the brown algae Undaria pinnatifida in certain food dishes. Certain types of brown algae, such as giant kelp, contain the chemical alginate. Manufacturers extract alginate from the algae to use as an emulsifier, binding agent or stabilizing compound. Alginate is commonly used in toothpaste, soap, canned meat and ice cream.